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Scientists have long known that climate change favors invasive species, but the pine beetle epidemic is far worse than they thought, extending from Canada, south through the Rockies and into southern California and New Mexico.

A new study, from the University of Colorado, Boulder, in The American Naturalist, spells out the grim facts:

"The current MPB epidemic is the largest in history, extending from the Yukon Territory, Canada, to southern California and New Mexico…. To date, more than 13 million ha [hectares] of trees have been killed in British Columbia. The MPB-killed trees in British Columbia alone will release 990 million tons of CO2 into the atmosphere, an amount equal to five times the annual emissions from all forms of transportation in the country. Forests affected by bark beetles also have altered hydrology and biogeochemical cycles. Thus, extensive beetle kill is altering forest ecology and tipping conifer forests from regional carbon sinks to carbon sources, thereby creating positive feedback for climate-change factors."